The present invention relates to a new and improved fin for a water ski which accomplishes three purposes: first, creating a "venturi" effect propels the ski as it performs certain turns and other maneuvers at a relatively greater rate of speed than a ski with a conventional fin or skeg; second, the application of a gradually tapering leading edge provides more positive edge control and stability for the ski in any attitude, particularly during turns; and third, the use of a tapering edge, culminating in an arch extending from one rail to the other at the rear of the ski that provides continuous contact with the surface of the water, and therefore greater control of the ski, during turning maneuvers, at angles of bank of up to 90.degree. relative to the surface of the water.
The commonly used water ski has a knife-like fin or skeg which extends approximately 41/2 inches below the surface of the ski. However, this type of fin loses contact with the water during turning maneuvers at angles of bank over approximately 45.degree., and at lesser angles of bank in rough water. In addition, skis with conventional skegs accelerate through the water only as a result of pressure applied through the skier's feet and legs and, ultimately, while there is constant tension on the skier's tow rope. Thus, during turns and other maneuvers which cause a decrease or cessation of tension on the tow rope, a water ski with a conventional skeg experiences a corresponding decrease or cessation of its speed through the water.
In the present invention a hollow, tapering "tunnel" is provided for attachment along the bottom rear portion of a water ski, with the generally U-shaped area in which the water enters the device being greater than the area of the generally O-shaped area where the water exits. Additionally, the leading edges or "rails" of the device taper gradually from the arch at the rear of the ski edges or "rails" of the device taper gradually from the arch at the rear of the ski and along the two outside edges of the ski until they terminate, flush with the ski bottom, as they approach the mid-point of the ski. A continuous flow of water along the bottom of the ski is directed along these leading edges or "rails" and into the aperture of the fin. As water passes into the increasingly narrow interior or "tunnel" portion of the fin, it necessarily will travel increasingly faster until it exits at the rearward aperture of the fin. In the process, the fin will provide a high degree of lateral and vertical stability, as well as a "venturi" effect which will cause the ski, as it performs turns and other maneuvers, to travel at a relatively greater rate of speed than a ski with a conventional skeg.
The present invention differs from other patented designs, including those in U.S. Pat. Nos. 2,704,043; 2,940,091; 3,020,568; 3,025,539; 3,052,899, 3,077,616; 3,229,312 and 3,255,472, the purpose of which is solely to re-direct water upward and in the process causes substantial drag without improving the performance of the ski. Instead, in the present invention, the flow of water continues uninterrupted along the longitudinal axis of the ski, thus creating no appreciable drag; the flow of water is directed by the edges or "rails" into the forward aperture of the fin; and the flow of water increases in speed from the point at which it enters the aperture of the fin tunnel until it exits the fin tunnel. Other designs which re-direct water flow upward provide merely aesthetic benefits, cause substantial drag, and provide none of the improved performance and handling properties of the present invention.
The present invention also differs from other patented designs, including those in U.S. Pat. Nos. 343,437; 3,089,157; and 3,103,673, because it incorporates venturi technology with a twin fin or arched fin design, with edges which taper forward gradually from the arch of the fin tunnel, following the outside edges of the ski until they gradually terminate, flush with the ski bottom, near the mid-point of the ski. The effect of these tapering edges, in conjunction with the fin tunnel, is to both provide increased edge control during turns, and also to direct water flow into the fin tunnel, thereby increasing the venturi effect. Other facially similar designs provide neither of these properties.
Accordingly, it is an object of the present invention to provide a new and improved water ski with arched fin which will overcome the shortcomings of the prior art water ski constructions.
Other objects, advantages, features and results will more fully appear in the course of the following description.